U.S. patent number 5,180,704 [Application Number 07/688,135] was granted by the patent office on 1993-01-19 for oil sorption with surface-modified rubber.
This patent grant is currently assigned to Regents of the University of Minnesota. Invention is credited to Wilhelm Reindl, Doil Williams.
United States Patent |
5,180,704 |
Reindl , et al. |
January 19, 1993 |
**Please see images for:
( Certificate of Correction ) ** |
Oil sorption with surface-modified rubber
Abstract
A method for sorbing oil comprises contacting the oil with an
oil sorbing article comprising a plurality of substantially
cross-linked polymer particles having adhesive layers formed on a
portion of the outer surfaces of a majority of the particles. The
particles are attached together with the adhesive areas to define a
plurality of interstitial spaces. The method further comprising
allowing the oil to sorb into the article. In the preferred
embodiment, the adhesive areas are formed by heating the portion of
the outer surfaces to a sufficient temperature to eliminate a
portion of the cross-linking. With the cross-linking eliminated,
the portion of the outer surfaces becomes tacky enabling adjacent
particles to adhere to one another and form the plurality of
interstitial spaces. The article comprises interstitial spaces to
trap air causing the article to remain on the surface of an aqueous
medium.
Inventors: |
Reindl; Wilhelm (St. Paul,
MN), Williams; Doil (Ramsey, MN) |
Assignee: |
Regents of the University of
Minnesota (Minneapolis, MN)
|
Family
ID: |
24763258 |
Appl.
No.: |
07/688,135 |
Filed: |
April 19, 1991 |
Current U.S.
Class: |
502/402;
264/109 |
Current CPC
Class: |
B01D
17/0202 (20130101); B01J 20/22 (20130101); C09K
3/32 (20130101); E02B 15/10 (20130101); C02F
1/681 (20130101); Y02A 20/204 (20180101) |
Current International
Class: |
C02F
1/68 (20060101); B01J 20/22 (20060101); C09K
3/32 (20060101); B01D 17/02 (20060101); E02B
15/04 (20060101); B01J 020/26 () |
Field of
Search: |
;502/402,401
;264/109 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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|
|
348491 |
|
Feb 1979 |
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AT |
|
3606356 |
|
Sep 1987 |
|
DE |
|
49-127889 |
|
Dec 1974 |
|
JP |
|
1075235 |
|
Jul 1967 |
|
GB |
|
Primary Examiner: Garvin; Patrick P.
Attorney, Agent or Firm: Kinney & Lange
Claims
What is claimed is:
1. A method for forming an article for sorbing oil, the method
comprising:
eliminating a portion of cross-linking of substantially
cross-linked polymer particles to form adhesive areas from the
particles on at least a portion of outer surfaces of a majority of
the particles; and
attaching the particles to each other using the adhesive areas to
define interstitial spaces between the attached particles.
2. The method of claim 1 wherein the step of eliminating comprises
heating the portion of the outer surfaces to a sufficient
temperature to eliminate cross-linking at the portion.
3. The method of claim 2 wherein the step of eliminating includes
abrading the particles to generate heat.
4. The method of claim 3 wherein the step of eliminating includes
forming the particles from a substantially cross-linked polymer
block.
5. The method of claim 4 wherein the step of eliminating comprises
cutting the polymer block with a suitable cutting apparatus.
6. The method of claim 5 wherein the step of eliminating includes
generating frictional heat from cutting the polymer block.
7. The method of claim 6 wherein the step of eliminating comprises
generating heat sufficient to eliminate cross-linking at the
portion substantially only from cutting the polymer block.
8. The method of claim 6 wherein the step of attaching comprises
displacing cut particles from a cutting element of the cutting
apparatus such that the particles contact and attach to each
other.
9. The method of claim 8 wherein the cutting apparatus is a
rotating blade and the step of attaching comprises displacing the
cut particles from the rotating blade as the blade rotates.
10. The method of claim 2 wherein the step of attaching comprises
the steps of compressing the particles together and then allowing
the particles to expand.
11. The method of claim 2 wherein the step of eliminating includes
heat generated from compression.
12. An article for sorbing oil, the article comprising:
a plurality of polymeric particles cross-linked substantially
throughout each particle and having adhesive area formed by
eliminating a portion of the cross-linking on a portion of outer
surfaces of a majority of the particles, the particles being
adhered together with the adhesive areas to define a plurality of
interstitial spaces.
13. The article of claim 12 wherein the cross-linking has been
eliminated through heating.
14. The article of claim 12 and oil consuming micro-organisms on
portions of the outer surfaces of the majority of particles.
15. The article of claim 12 wherein the article floats on an
aqueous medium.
16. The article of claim 12 wherein the particles comprise
rubber.
17. The article of claim 16 wherein the particles are formed from
rubber tires.
18. The article of claim 16 wherein the article is a fluffy mass
approximately 0.2 millimeter to 1 centimeter in length.
19. The article of claim 16 wherein the rubber particles are
approximately of size 10 mesh and smaller.
20. The article of claim 16 wherein the article is cylindrical in
shape.
21. A floatable article for sorbing oil from the surface of an
aqueous medium, the article comprising:
a plurality of cross-linked rubber particles having adhesive areas
formed by eliminating a portion of the cross-linking on a portion
of outer surfaces of a majority of the particles, the particles
attached together with the adhesive areas to define a plurality of
interstitial spaces.
22. The article of claim 21 wherein the particles are formed from
rubber tires.
23. The article of claim 22 wherein the article adsorbs the oil
into a portion of the interstitial spaces wherein the oil is
received and retained on the outer surfaces of the particles
forming the portion of the interstitial spaces.
24. The article of claim 23 wherein the oil is a medium weight
crude oil and the article exhibits by weight adsorption
capabilities of the oil approximately 3:1.
25. The article of claim 22 wherein the oil is a medium weight
crude oil and the article exhibits by weight sorption capabilities
of the oil approximately 8:1 when the article is exposed to the oil
for a sufficient length of time such that the oil penetrates into
the rubber particles.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an article for oil sorption, and
more particularly, to an article having a plurality of interstitial
spaces formed from a plurality of adhered cross-linked polymer
particles and to a method for making the same.
2. Description of the Prior Art
Contaminated surfaces resulting from spilled oil pose a severe
threat to the environment. Such oil spills are found both on land
and water. Oil pools collect around above ground storage tanks and
in the ground around under ground storage tanks and oil
transportation pipes. Oil spills also occur from tanker and
underwater oil drilling accidents as well as smaller spills in
harbors, rivers, waterways and other navigation channels resulting
from the daily loading, unloading and storage of oil throughout the
world.
Oil spills on water bodies are particularly serious. Besides
contaminating the surface of the water body and posing a
significant risk to waterfowl, surface oil invariably reaches and
contaminates the adjoining land. Even if the adjoining land is not
contaminated, with time, the oil will settle as conglomerates at
the bottom of the water body, thus destroying plants and other
forms of aquatic life.
Various methods have been proposed and used for removing spilled
oil from both land and water. These methods include mechanical
skimmers, microorganisms that consume the spilled oil, and
detergents. Skimmers require complex machinery; microorganisms can
only be used within narrow environmental constraints, and
detergents pose other environmental hazards. In view of these
drawbacks, sorbent articles are increasingly becoming the preferred
method of recovering spilled oil. Such sorbent articles and
materials presently used include straw and ground corn cobs, some
mineral adsorbents like perlite, and clays, as well as oil
absorbing polymers.
It has been known for sometime that vulcanized rubber and other
types of cross-linked polymers will absorb oil and organic vapors
to a varying degree. Examples of such use are disclosed in U.S.
Pat. No. 4,728,343 issued to Syder, U.S. Pat. No. 3,567,660 issued
to Winkler, U.S. Pat. No. 4,039,489 issued to Fletcher et al. and
U.S. Pat. No. 4,182,677 issued to Bocard et al.
U.S. Pat. No. 4,728,343 discloses a method of absorbing organic
vapors in a storage container by suspending ground rubber particles
in a mesh net. The rubber particles absorb the vapors so that the
vapor concentration does not approach an explosive level.
U.S. Pat. No. 3,567,660 discloses a method for absorbing oil spills
with shredded or ground rubber from automobile tires. The tires are
ground to a particle size between 1 and 10 mesh. The Winkler patent
teaches that rubber particles larger than 1 mesh have a tendency to
sink in water, while particles smaller than 10 mesh dissolve
quickly in oil. When the shredded rubber particles are applied to
spilled oil on a contaminated water surface, the particles swell
from the imbibed oil and coagulate to form conglomerates. In the
preferred embodiment, the shredded rubber tires are combined with
powdery polystyrene. The Winkler patent teaches that this addition
speeds absorption of the spilled oil.
U.S. Pat. No. 4,039,489 discloses a method for absorbing oils with
polymer particles having a minimal amount of cross-linking. In the
preferred embodiment, the mean chain length of the polymer between
cross-linking sites is recommended, at a minimum, to be at least
4,000 chain atoms long. Although the Fletcher et al. patent teaches
that minimal cross-linked polymers absorb oil readily, the
resulting absorbent is physically weak when swollen with oil. When
used to absorb an oil spill on water, the polymer tends to break
apart. To overcome this problem, the Fletcher et al. patent teaches
coating a fiber or fabric substrate with the minimal cross-linked
polymer. The fiber substrate provides a support structure.
Another method for producing oil absorbing polymers is disclosed in
U.S. Pat. No. 4,182,677. This patent teaches that rubber particles
of the size 0.1 to millimeters can readily absorb hydrocarbons or
organic liquids if the particles are first subjected to organic or
inorganic acid solvents. The patent teaches that rubber particles
are created by using crushers or by grinding the rubber waste after
cooling it to a very low temperature, for example, in liquid air.
To enhance the absorption of oil, the rubber particles are treated
with a mineral or organic acid. The rubber particles are stored in
suspension in a pure acid or diluted acid solution. After
filtration, the rubber particles are washed with water in order to
remove the acid. In U.S. Pat. No. 4,182,677, the treated rubber
particles are stirred in suspension with a mechanical stirrer or
through convenient shaping of the container apparatus. The patent
teaches that it is advantageous to use rubber waste of a density
lower than 1.5 so that, after the hydrocarbons have been absorbed,
the rubber particles rise to the surface.
SUMMARY OF THE INVENTION
The present invention provides an improved oleophylic article. The
article comprises a plurality of substantially cross-linked
polymeric particles adhered together on a portion of outer surfaces
of a majority of the particles. The adhered particles define a
plurality of interstitial spaces. The interstitial spaces trap air
within the article during sorption of a spilled oil body and
prevent the article from sinking in an aqueous medium.
The present invention further provides a method for making the
oleophylic article. The method comprises: working substantially
cross-linked polymer particles to form adhesive areas on at least a
portion of outer surfaces of a majority of the particles; and
adhering the particles using contacting adhesive areas to define
interstitial spaces between the joined particles. In the preferred
embodiment, the step of working comprises eliminating a portion of
the cross-linking on the portion of the outer surface area of the
particle to which the adjacent particle is attached. With the
cross-linking at least partially eliminated, the corresponding
outer surfaces become tacky enabling the particles to adhere and be
attached.
The present invention is equally suited for sorption of oil in
aqueous and non-aqueous situations. In either case, the method for
sorbing oil comprises contacting the oil with the article of the
present invention having a plurality of interstitial spaces defined
by particles attached together with adhesive areas. When used in an
aqueous solution, the interstitial spaces trap air pockets which
allow the article to float on the surface of the solution during
and after oil sorption.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a first embodiment of an oleophylic
article of the present invention;
FIG. 2 is a fragmentary sectional view of the article taken as on
line 2--2 in FIG. 1;
FIG. 3 is a schematic representation of a cutting apparatus
comprising a rotating saw blade for producing the article in FIG.
1;
FIG. 4 is a schematic representation of improvements to the cutting
apparatus in FIG. 3;
FIG. 5 is a sectional view of a pressing apparatus for producing a
second embodiment of the oleophylic article of the present
invention;
FIG. 6 is a front plan view representation of the pressing
apparatus in FIG. 5;
FIG. 7 is a perspective view of the second embodiment of the
oleophylic article of the present invention;
FIG. 8 is a fragmentary top plan view of the rotating saw blade
taken as on line 8--8 in FIG. 3;
FIG. 9 is a sectional view of the rotating saw blade taken as on
line 9--9 in FIG. 8; and
FIG. 10 is a view of a second cutting apparatus for producing the
first embodiment of the oleophylic article of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a perspective view of an oleophylic article, generally
indicated at 20, made according to the present invention. Article
20 comprises a plurality of substantially cross-linked polymer
particles, such as particles 22A, 22B, 22C, 22D and 22E, adhered
together at a plurality of adhesive areas such as 24A, 24B, 24C and
24D and remaining unattached at other areas. Adhesive areas 24A
through 24D secure particles 22A through 22E together on respective
outer surface portions while leaving other surface areas spaced to
form a plurality of interstitial spaces or air voids such as 26A,
26B and 26C. The particle surfaces defining the plurality of
interstitial spaces and the cross-linked polymer particles
themselves provide article 20 with the ability to both adsorb and
absorb oil. The term "oil" as used herein is to be construed as
meeting the definition of the term as found in Hackh's Chemical
Dictionary, 4th Edition, McGraw-Hill, Inc., New York, 1969.
As illustrated in FIG. 2, article 20 comprises additional particles
such as particles 32A and 32B which comprise other outer surface
portions of article 20, as well as particles 32C, 32D and 32E, by
way of example, which are attached to outer surface particles 22A,
22B, 32A or 32B, or to other outer surface particles and inner
particles, not shown. As with particles 22A through 22E, particles
32A through 32E are substantially cross-linked polymer particles
adhered to adjacent particles at a plurality of adhesive areas 34A,
34B, 34C, 34D and 34E. As shown in the preferred embodiment of
FIGS. 1 and 2, adhesive areas 24A through 24D and 34A through 34D
are formed on a small portion of each respective particle outer
surface. Interconnection of particles 22A, 22B and 32A through 32E
at spaced locations while leaving other locations unattached define
a plurality of interstitial spaces 38A, 38B, 38C and 38D which are
used to retain portions of an oil body 40 therein. Although
illustrated in FIG. 2 with only a maximum of three bonds for each
particle, it is understood that each particle forming article 20 is
connected to one or a plurality of adjacent particles with one or a
plurality of adhesive bonds.
Analysis indicates that article 20 sorbs oil body 40 through both
adsorption and absorption. Upon initial contact with oil body 40,
the outer surfaces forming each interstitial space 38A through 38D
are believed to adsorb oil and form a continuous oil film 42 on the
surfaces defining such spaces, within each corresponding
interstitial space, thereby trapping air in the interstitial
spaces. A plurality of air pockets such as 44A, 44B, 44C, 44D and
44E are thus formed within article 20. With time, a portion of oil
film 42 penetrates the outer surfaces of particles 22A, 22B and 32A
through 32D to be absorbed within each corresponding polymeric
particle. Absorption of oil film 42 causes swelling of the
substantially cross-linked polymeric particles 22A, 22B, and 32A
through 32D, which in turn is believed to further increase the
strength of adhesive bonds 34A through 34D.
When article 20 has sorped a quantity of oil, the article 20 forms
a conglomerate that is readily manageable. As illustrated in FIG.
1, due to the trapped air pockets such as 44A through 44E
illustrated in FIG. 2, article 20 will remain afloat above a water
body 46 during and after oil sorption.
In addition to the sorption capabilities described above, article
20 can be combined with other known oil spill control. For example,
a flame retardant chemical such as sodium molybdate can be applied
to the article in order to reduce the possibility of oil fires. In
addition, oil consuming microorganisms such as those from Cybron
Chemicals Inc. of Birmingham, N.J., can be applied to portions of
the outer surfaces of a majority of the adhered particles. The
present invention provides a structure that protects the
micro-organisms from dispersement when the water body is
agitated.
Nutrients such as nitrogen and phosphorus can be added to the
structure to enhance micro-organism oil comsumption. Such nutrients
are readily dissolvable in an oil base or medium, as for example,
Inipol EAP 22 from Exxon Research and Engineering Co. of Annandale,
N.J. which is a source of nitrogen. In the preferred embodiment,
the oil medium along with the dissolved nutrients would be absorbed
within the polymer structure of a majority of the particles.
Absorption is limited in that the particles are not completely
saturated with the oil based nutrients. Partial saturation of the
particles enables the particles to absorb additional oil when the
article is placed on an oil spill while diffusion of nutrients from
within the particles to the outer surface provides the
micro-organisms with nutrients at a gradual rate.
In the practice of the present invention, a wide variety of
cross-linked or vulcanized materials may be employed. Such
vulcanized materials are readily available as processing scrap,
particularly from tires, and for purposes of the invention, the
stocks are based on natural rubber, or on any of the synthetic
rubbers used in the tire industry, for example, SBR, butyl rubber,
or polychloroprene or mixtures thereof. Conventional tire sidewall
stocks and tire tread stocks are equally suitable.
Scrap tires are preferably used in the instant invention and, as
noted above, scrap tires comprise standard vulcanizable materials
(i.e., rubber capable of cross-linking) which are compounded and
vulcanized in accordance with the standard procedures known in the
industry. The vulcanizable materials are any of the unsaturated
hydrocarbon polymers exemplified by the diene polymers (which may
be halogenated), such as polybutadiene, polychloroprene or
polyisoprene, especially polybutadiene or polyisoprene having a low
or high content of cis-polymer; copolymer rubbers such as SBR
(copolymer of styrene and butadiene), butyl rubber (copolymers
based on isomonoolefins such as isobutylene and a small amount,
e.g., 0.25 to 105 of a conjugated diene such as isoprene), and even
natural polymers such as guayule rubber, Hevea rubber and the like.
Also depolymerized rubber may be used.
Other unsaturated useable hydrocarbonic polymers are the rubbery
interpolymers of at least two alpha-monoolefins (e.g., ethylene,
propylene, butene-1, hexene-1, 4-methylpentene-1, 5-methylhexene-1,
4-ethylhexene-1 or similar olefins having the formula CH.sub.2
=CHR, in which R is hydrogen or a hydrogen radical, particularly a
saturated alkyl hydrocarbon radical having from 1 to 8 carbon
atoms) and at least one copolymerizable diene such as
dicyclopentadiene, methylcyclopentadiene dimer, 1,4-hexadiene,
11-ethyl-1, 11-tridecadiene, 1,9-octadecadiene, 1,5-cyclooctadiene,
methylene norbornene, ethylidene norbornene or other suitable
dienes (such rubbers are sometimes referred to as "EPDM").
Terpolymers of the kind recited in the preceding sentence contain
from about 1 to 25% (more preferably about 2 to about 15%) by
weight of dicyclopentadiene or the like are preferred.
The invention can be practiced with rubbers prepared by methods
other than solution polymerization, such as, for example, by
emulsion polymerization. Typical of such rubbers are emulsion
polymerized diene homopolymers or copolymers including
butadiene-styrene copolymer or copolymers with other
copolymerizable monomers such as acrylonitrile, vinylpyridine,
ethyl acrylate and the like.
The amount of scrap rubber or other types of substantially
cross-linked polymer to be prepared as the oleophylic article of
the present invention is dependent upon the amount of oil to be
sorbed. This amount will vary from case to case; however,
determination of the amount is within the knowledge of persons
skilled in the art. The selection depends on the circumstances.
As described above, the adhesive areas of article 20, such as areas
34A through 34E, connect each of the particles to an adjacent
particle to define the plurality of interstitial spaces. In
general, article 20 is formed by a method comprising: working the
substantially cross-linked polymer particles to form adhesive areas
on at least a portion of outer surfaces of a majority of the
particles; and attaching the particles to each other using the
adhesive areas to define the interstitial spaces between the
attached particles.
"Working" is defined as any step or succession of steps to produce
the adhesive areas. In the preferred embodiment, this step
comprises eliminating a portion of the cross-linking on the portion
of the outer surface to which the adjacent particles are attached.
With the cross-linking eliminated, the outer surface is tacky,
enabling the area to be secured to another adhesive area as well as
those areas in which the cross-linking substantially remains. In a
further preferred embodiment, the particle surfaces are softened by
heating the outer surface portions to a temperature that alters or
breaks the cross-linking sites. This definition of "working" is
understood to include all processes known in the art to
"de-vulcanize" or break cross-linking in cross-linked polymers.
Furthermore, it is within the scope of the present invention to use
a separate suitable adhesive that can adhere the particles
together. Characteristics of such an adhesive include substantial
insolubility to the oil to be sorbed and the ability to apply the
separate adhesive to at least a portion of a majority of the
plurality of substantially cross-linked polymer particles.
FIG. 3 illustrates the preferred method of processing cross-linked
polymer blocks, such as used rubber tire tread or sidewall stock,
into the oleophylic article 20 shown in FIGS. 1 and 2. Referring to
FIG. 3, the cross-linked rubber block 50 is placed on support
member 52 to engage a cutting apparatus 48. In the preferred
embodiment, cutting apparatus 48 comprises a rotating saw blade 54
or a plurality of saw blades, each having a plurality of cutting
teeth 46. Saw blade 54 rotates on an axis 55 and is powered from
any suitable power source, not shown. In a conventional manner,
block 50 is moved against rotating blade 54 with a suitable rate to
cut a 55A therein. As each cutting edge of the plurality of teeth
46 engages a portion of block 50, frictional heat generated during
the process of abrasively cutting with teeth 46 works, at least a
portion of the outer surfaces of the particle being cut. The
frictional heat raises the temperature of the outer surface of the
cut particle to a temperature sufficient to de-vulcanize or
eliminate at least a portion of the cross-linking between the
polymer molecules at the surface of a majority of the particles
being cut.
With the outer surface cross-linking eliminated, the corresponding
outer surface portion of the cut particle is tacky. Continued
rotation of blade 54 propels the particles having tacky outer
surfaces toward other previously cut (and tacky) particles. Such
previously cut particles can reside in relief spaces 57 between the
plurality of teeth 46 or on an impact plate 60 located proximate to
rotating blade 54. The particles are propelled from blade 54
because of the centrifugal force generated as blade 54 rotates. The
cut particles impinge upon other previously cut particles with the
tacky outer surfaces of the majority of the particles contacting
surfaces of adjacent particles. The force of impingement is
sufficient to form the adhesive bonds using the adhesive areas such
that the particles are attached in a random manner as shown in FIG.
2. The adhered particles are removed from plate 60 at a sufficient
rate to prevent the build up of heat which could lead to additional
(and excessive) de-vulcanization or cross-linking elimination of
the particles.
In the preferred embodiment, blade 54 comprises a "cross-cut" saw
of conventional design having the plurality of teeth 46 on blade 54
arranged as shown in FIGS. 8 and 9. FIG. 8 is a fragmentary top
plan view of blade 54 showing two sequential teeth 100 and 101 of
the plurality of teeth 46. Tooth 100 comprises a cutting edge 102
that is angled back from a leading point 104 at an angle 103 of
approximately 75.degree. with reference from a side top surface
edge 106. Tooth 101 is substantially similar to tooth 100 except
that tooth 101 comprises a cutting edge 108 that is opposite to
that of cutting edge 102. As shown in FIG. 8, cutting edge 10B
angles back from a leading point 110 at an angle 111 approximately
75.degree. from an opposite side top surface edge 112.
FIG. 9 is a sectional front plan view of cross-cut blade 54. FIG. 9
shows that cutting edges 102 and 108 are also angled down opposite
to one another from leading points 104 and 110, respectively. Each
cutting edge 102 and 108 forms an angle 114 and 115 of
approximately 75.degree. between corresponding opposite side
surfaces 116 and 117.
Analysis indicates that inclination of the cutting edges from a
corresponding leading point allows the cross-cut saw to cut the
polymer block with minimal tearing. Other rotating blades, such as
a dado blade have been used on cutting apparatus 48; however, such
a blade has a cutting edge that is neither angled downwardly nor
backwardly from a leading point. When used on cutting apparatus 48,
it is believed the dado blade strikes the polymer block laterally
along the cutting edge and tears rather than cuts the particles
from the polymer block. Such tearing does not appear to generate
enough frictional heat to eliminate the cross-linking on portions
of the outer surface of a majority of the particles. Without
elimination of the cross-linking, the cut particles do not adhere
to each other to form interstitial spaces and will sink when placed
on an aqueous medium. When the dado blade was modified to include
an angled cutting edge, adhered particles of the present invention
were produced.
Improvement to the method shown in FIG. 3 are shown in FIG. 4.
Referring to FIG. 4, a lubricant 62 is sprayed on blade 54 as teeth
46 rotate to cut block 50. Lubricant 62 reduces the frictional heat
developed on side surfaces 64 of blade 54 thus preventing block 50
from adhering to blade 54. Lubricant 62 allows teeth 46 to engage
block 50 and work the outer surface portions of the cut particles
at an increased rate. Lubricant 62 may comprise water, or any
suitable non-detergent oil or combination thereof. In the preferred
embodiment, lubricant 62 is sprayed from a nozzle 66 of
conventional design. Centrifugal force propels lubricant 62 toward
teeth 46 along side surfaces 64 as blade 54 rotates.
FIG. 4 further shows a conveyor assembly 51 to receive particles
cut but cutting apparatus 48. Conveyor assembly 51 comprises a belt
59 secured around opposed roller assemblies 53 that are driven by a
suitable power source, not shown. Belt 59 receives both adhered
particles and unadhered particles from cutting apparatus 48, and
provides a suitable impingement surface upon which additional
particles may be adhered to each other. Conveyor assembly 51
transfers the adhered particles to a remote collection location
63.
A second preferred method for forming oleophylic article 20 having
the interstitial spaces of FIGS. 1 and 2 is shown in FIGS. 5 and 6
as a pressing apparatus 70. Pressing apparatus 70 comprises a block
72 having a cylindrical opening 74. Block 72 is secured at one end
to a support plate 76 to form an enclosure or container for a
plurality of substantially cross-linked particles 78 which have
been precut or ground to a suitable size. A piston 80 is positioned
within opening 74 and is moveable to compress particles 78 within
opening 74. In the preferred embodiment, a suitable orifice 82 is
provided to allow compressed particles to exit apparatus 70.
In operation, block 72 is heated to a temperature slightly below
the temperature at which the cross-linking is eliminated on the
outer surfaces of a majority of particles 78. As piston 80 is
displaced within opening 74 toward support plate 76 to compress
particles 78, additional heat is generated. The additional heat
raises the outer surface temperature of a majority of particles 78
above the temperature sufficient to de-vulcanize or eliminate
cross-linking and form the adhesive surface areas. Since pressure
from piston 80 is maintained, the compressed particles 78 are
forced through orifice 82. As compressed particles 78 are forced
through orifice 82, additional heat is worked on the outer surfaces
of the particles to form additional adhesive areas that in turn
adhere to opposed surfaces of adjacent particles. Once exiting
orifice 82, the adhered particles expand and break some of the
adhesive bonds to form an oleophylic article 90 shown in FIG. 7.
Article 90 is cylindrical in shape but includes interstitial spaces
similar to spaces 38A through 38D shown in FIG. 2. The size and
shape of article 90 can be selectively altered by varying the size
and shape of orifice 82.
Another cutting apparatus 119 suitable for forming the oleophylic
article of FIGS. 1 and 2 is shown in FIG. 10 comprising a grinding
drum 120. Referring to FIG. 10, the cross-linked rubber block 50 is
placed in a cylinder 122 having a piston 124 which is movable under
power. In this embodiment, grinding drum 120 comprises a plurality
of grinding teeth that are randomly spaced along an outside surface
126. Drum 120 rotates around a drum axis 128A powered from any
suitable power source, not shown. Block 50 is directed against
rotating drum 120 with suitable pressure from piston 124 to grind
an end 128 of block 50. As grinding surface 126 contacts block end
128, frictional heat present during the process of abrasively
cutting or grinding block 50 works at least a portion of the outer
surface of the particles being cut. The frictional heat raises the
temperature of the outer surface of the cut particle to a
temperature sufficient to de-vulcanize or eliminate at least a
portion of the cross-linking between the polymer molecules at the
surface of a majority of particles being cut.
With the cross-linking eliminated, the corresponding outer surface
portion of the cut particle is tacky. Continued rotation of drum
120 propels the particles having tacky outer surfaces towards other
previously cut and tacky particles 129. Such previously cut
particles typically are located on an impact plate 130 located
proximate to rotating drum 120. The particles are propelled from
grinding surface 126 because of the centrifugal force generated as
drum 120 rotates. The cut particles impinge upon other previously
cut particles with the tacky outer surfaces of the majority of the
particles contacting surfaces of adjacent particles. The force of
impingement is sufficient to form the adhesive bonds using the
adhesive areas such that the particles are attached in a random
manner as shown in FIG. 2. The adhered particles are removed from
plate 130 at a sufficient rate to prevent the build up of heat
which could lead to additional (and excessive) de-vulcanization or
cross-linking elimination of the particles.
Particle production is increased with a lubricant 62 sprayed on
grinding surface 126 from nozzle 66 of conventional design.
Lubricant 62 prevents excessive heat from being generated which can
lead to excessive de-vulcanization of the particles. Lubricant 62
may comprise water, any suitable non-detergent oil or combination
thereof.
To further increase particle production impact plate 130 may be
replaced with conveyor assembly 51 shown in FIG. 4. Conveyor
assembly 51 receives the particles from drum 120 and transfers the
adhered particles to a remote collection location.
The following non-limitative examples illustrate production of the
oleophylic article of the present invention according to the
methods disclosed above. Additional examples are provided for oil
sorption capabilities in aqueous and non-aqueous mediums.
EXAMPLE 1
An oleophylic article mass in accordance with the present invention
was made generally as illustrated in FIG. 3. Cutting apparatus 48
comprises a 10 inch table saw manufactured by Rockwell
International Corporation of Pittsburgh, Penna. The saw rotates a
32 tooth cross-cut, carbide tipped cutting blade at 4,200 rpm. The
blade was set for a cutting depth of 1/4 of an inch. A Uniroyal,
steel-belted "Tigerpaw" radial tire, size P205/75R14, (TPC Spec.
SPC. 1025 MS) was placed on the table saw and cut randomly on the
tread and sidewall stock. Sufficient pressure was applied to the
tire to initiate and maintain tire cutting without excessive smoke
being produced. The cut particles were retrieved from a
manufacturer installed U-shaped deflector plate mounted to the
table saw forward of the saw blade and below the table support
member.
The cut particles formed fluffy masses of various sizes from
approximately 0.2 millimeters to one centimeter. When viewed under
a microscope, a majority of the particles were attached to adjacent
particles to define a large number of interstitial spaces. Outer
surfaces of the particles appeared "glassy" which indicated melting
or softening of the rubber. When placed on a water surface, the
particle masses remained afloat.
EXAMPLE 2
Using the equipment in Example 1, a lubricant comprising by volume
approximately 50% water and 50% 30 weight non-detergent oil was
sprayed on the saw blade during cutting as illustrated generally in
FIG. 4. The lubricant allowed random cuts in the tread and side
wall stock of the tire of Example 1 at an increased rate with
minimal cutting smoke. The cut particles formed masses which
exhibited the physical characteristics described above in Example
1.
EXAMPLE 3
An oleophylic article shown in FIG. 7 was made generally as
illustrated in FIG. 5. Pressing apparatus 70 comprised a brass
block having a two inch diameter cylindrical opening. Four
V-channeled grooves, approximately 1/16 of an inch on edge, were
cut into an end of the block. A brass plate was secured to the same
end of the block to form four V-channeled orifices.
Precut, unadhered used rubber tire particles (size 10 mesh and
smaller) from Trash Depo Inc. of Moorhead, Minn., were placed
within the block opening. A 2 inch aluminum piston was placed on
top of the particles and in the opening. The brass block was heated
approximately to 600.degree. F. The heated block and piston were
placed under a hydraulic press. A pressure of 200 psi was applied
to the piston to force the compressed particles through the
orifices. The particles expanded after exiting the orifices as a
mass to a cylindrical shape having a diameter of 1/4 of an inch.
Interstitial spaces were located within the article while outer
surfaces of the particles appeared glassy which indicated
de-vulcanization or cross-linking elimination at the outer surfaces
of the particles. When placed on a water surface, the article
remained afloat.
EXAMPLE 4
The precut unadhered rubber particles described in Example 3 were
placed within the block opening of the pressing apparatus of
Example 3. The block was heated to approximately 400.degree. F. A
pressure of 200 psi was applied with the hydraulic press and piston
to force compressed particles through the orifices. The particles
expanded after exiting the orifice. However, outer surfaces of the
particles did not appear glassy to indicate any de-vulcanization.
The particles were loosely attached and sank when deposited on a
water surface.
EXAMPLE 5
The precut unadhered rubber particles described in Example 3 were
placed within the block opening of the pressing apparatus of
Example 3. The block was heated to approximately 800.degree. F. A
pressure of 200 psi was applied with the hydraulic press and piston
to force compressed particles through the orifices. Outer surfaces
of the resultant particle mass did appear glassy to indicate
de-vulcanization, however, the mass was hard with little
resiliency. Interstitial spaces were not observed within the
article.
EXAMPLE 6
The precut unadhered rubber particles described in Example 3 were
placed within the block opening of the pressing apparatus of
Example 3. The block was heated to approximately 600.degree. F. A
pressure of 200 psi was applied with the hydraulic press and piston
however, the compressed particles were not allowed to exit the
orifices. Pressure was maintained until the block temperature had
cooled. The resultant article was removed from the opening. Outer
surfaces of the particles appeared glassy to indicate
de-vulcanization. Interstitial spaces were not observed within the
article. When placed on a water surface, the article sank.
EXAMPLE 7
An oleophylic article mass in accordance with the present invention
was made generally as illustrated in FIG. 10. Cutting apparatus 119
comprised a grinding drum 8 inches in length and 8 inches in
diameter that was rotated at 3600 rpm from a 25 HP electric motor.
The grinding surface on the grinding drum comprised 1/16 inch
through 1/4 inch carbide chips randomly distributed throughout the
grinding surface and bonded to the drum with a stainless steel
matrix. Tire stock from the used rubber tire of Example 1 was
placed in a feed plunger 8 inches in length and 4 inches wide. The
feed plunger was connected to an air compressor and directed the
tire stock against the rotating drum at a rate of approximately 1.3
feet per minute. A cooling spray comprising a fine mist of water
was sprayed on the rotating drum during the grinding at a rate of
1/20 of a gallon per minute.
The tire stock was applied to the rotating grinding drum with an
estimated contact pressure of 20 psi. The contact pressure is an
estimate due to compression of the tire stock in the feed plunger
and the general inability to directly measure contact pressure.
Approximately 60% of the ground tire stock formed fluffy masses of
various sizes having interstitial spaces. The remainder appeared to
be hard, solid particles. When placed on a water surface, the hard
solid particles sank while the fluffy masses remained afloat.
EXAMPLE 8
Using the cutting apparatus and tire stock described in Example 7,
the tire stock was applied to the rotating grinding drum with an
estimated contact pressure of between 5 and 15 psi. Approximately
80% to 90% of the ground tire stock formed fluffy masses having
interstitial spaces while the remainder formed hard solid
particles.
EXAMPLE 9
The oil adsorption capabilities of the adhered particle mass
prepared in Example 1 were approximated with the following test
method. Two 400 milliliter beakers were partially filled with tap
water. Measured amounts of a medium weight crude oil were added to
each beaker and allowed to separate as an oil surface body.
Measured amount of the particle mass of Example 1 were then added
to each beaker. The particle masses were stirred with medium weight
crude oil and allowed to stand. By weight, each beaker
comprised:
TABLE 1 ______________________________________ BEAKER 1 BEAKER 2
______________________________________ A) Water 187.41 g 190.87 g
B) Crude Oil 13.09 g 14.57 g C) Particle Mass 3.27 g 4.86 g Ratio
of B/C 4:1 3:1 ______________________________________
The following results were obtained. In beaker 1, the particle mass
immediately adsorbed the medium weight crude oil except for a very
thin film which remained on the water surface. This oil film was
present in beaker 1 after 15 minutes. In beaker 2, the particle
mass also immediately adsorbed the oil except for a thin layer that
remained on the water surface after stirring. However, unlike the
thin oil film present in beaker 1, the thin oil film present in
beaker 2 disappeared within 5 minutes after stirring. The particle
mass and oil mixture formed a large conglomerate in both beakers.
The conglomerate remained afloat during and after oil
adsorption.
From the foregoing example, the particle mass exhibits by weight
adsorption capabilities of a medium weight crude oil approximately
3:1.
EXAMPLE 10
The oil sorption capabilities of the particle mass prepared in
Example 1 were approximated with the following test method. Two 600
milliliter beakers were partially filled with tap water. Measured
amounts of a medium weight crude oil were added to each beaker and
allowed to separate as an oil surface body. Measured amounts of the
adhered particle mass of Example 1 were then added to each beaker.
By weight each beaker comprised:
TABLE 2 ______________________________________ BEAKER 1 BEAKER 2
______________________________________ A) Water 387.15 g 403.46 g
B) Crude Oil 14.83 g 21.31 g C) Particle Mass 6.65 g 2.65 g Ratio
of B/C: 2.23:1 8.04:1 ______________________________________
The following results were obtained. After gently stirring three
times during a 20 hour test period, the particle mass of beaker 1
formed a conglomerate that remained afloat and which sorbed all the
oil except for a small amount that remained attached to the side of
the beaker. The mixture of beaker 2 was gently stirred 10 times
during the same 20 hour test period. After 20 hours, all the oil
had been sorbed by the particle mass and formed a conglomerate that
remained afloat. With slight agitation, a thin oil film reappeared
on the water surface of beaker 2.
From this example, it is shown that the particle mass exhibits a
sorption ratio by weight of about 8:1 with medium weight crude oil
when exposed for sufficiently long times so that the oil penetrates
into the rubber substrate in distinction to shorter exposure times
(e.g. Example 9) where sorption is primarily in the interstitial
spaces.
EXAMPLE 11
The sorption capabilities of the adhered particle mass prepared in
Example 1 for a low temperature and deposited on an aqueous
solution including sodium chloride were studied with the following
method. A 600 milliliter beaker was partially filled with water
comprising 3.5% sodium chloride. The temperature of the solution
was lowered to 0.degree. C. and a measured amount of medium weight
crude oil of the same temperature was added and allowed to separate
as an oil surface body. At 0.degree. C. it was observed that some
ice chunks did exist within the solution. A measured amount of
particle mass of Example 1 was then added to the beaker and stirred
gently and allowed to stand. By weight, the beaker comprised:
TABLE 3 ______________________________________ A) Water 347.24 g -
3.5% NaCl at 0.degree. C. B) Crude Oil 15.44 g at 0.degree. C. C)
Particle Mass 5.10 g Ratio of B/C 3:1
______________________________________
The sodium chloride aqueous solution, the lower temperature of that
solution and the presence of ice in the beaker did not appear to
inhibit either sorption of the medium weight crude oil by the
particle mass or flotation of the mass after oil sorption. Although
the viscosity of the crude oil had increased due to the lower
temperature of the crude oil as compared to the previous examples,
rate of sorption of crude oil was similar to the rate observed in
beaker 2 of Example 10.
EXAMPLE 12
The oil sorption capabilities of the adhered particle mass prepared
in Example 3 were approximated with the following test method. One
400 milliliter beaker was partially filled with 186.9 grams of tap
water. 18.2 grams of a medium weight crude oil was then added to
the beaker and allowed to separate as an oil surface body. 3.26
grams of the particle mass of Example 3 was added and stirred
gently with the medium weight crude oil and allowed to stand.
After the particle mass had been exposed to the crude oil for 3
minutes, the mixture was drained on a wire screen of 10 mesh for 3
minutes. The resultant particle mass weighed 14.07 grams
corresponding to oil sorption of 10.76 grams. By weight, the
sorption ratio of the particle mass of Example 3 relative to oil
was approximated at 3.3 to 1.
EXAMPLE 13
The oil sorption capabilities of the adhered particle mass prepared
in Example 7 were approximated with the following test method. One
400 milliliter beaker was partially filled with 182.53 grams of tap
water. 20.1 grams of a medium weight crude oil was then added to
the beaker and allowed to separate as an oil surface body. 4.35
grams of the fluffy particle mass of Example 8 was added and
stirred gently with the medium weight crude oil and allowed to
stand.
After the particle mass had been exposed to the crude oil for three
minutes, the mixture was drained on a wire screen of 10 mesh for
three minutes. The resultant particle mass weighed 19.57 grams
corresponding to oil sorption of 15.22 grams. By weight, the
sorption ratio of the particle mass of Example 8 relative to oil
was approximated at 3.5 to 1.
EXAMPLE 14
The barrier capabilities of the present invention in a non-aqueous
medium are shown in the present example. A perforated plate, two
inches wide and 11 inches in length having 1/4 inch holes on one
inch centers, was supported one inch above the bottom of an 18 inch
clear, rectangular, acrylic container having inside base dimensions
equal to that of the perforated plate. Above the perforated plate,
the container comprised the following layers: a bottom layer of
silica sand (30 mesh) six inches in height; a one inch layer of
adhered particle mass prepared as disclosed in Example 1; and a top
layer of silica sand (30 mesh) six inches in height.
A two inch layer of medium crude oil was poured on top of the top
layer of sand and allowed to percolate through the top layer. The
medium crude oil reached the adhered particle mass layer after
2-1/2 minutes. Although the container was allowed to stand for two
days, the crude oil did not percolate through the particle mass
layer to the underlying bottom layer of sand.
EXAMPLE 15
The rectangular container was refilled as described in Example 14
with a bottom layer of silica sand, an interposed layer of adhered
particles prepared as disclosed in Example 1 and a top layer of
sand. A five inch layer of medium weight crude oil was poured on
the top layer of sand and allowed to percolate therethrough. The
crude oil again reached the particle mass layer in 2-1/2 minutes.
The container was allowed to stand for two days, however, the crude
oil did not percolate through the particle mass layer.
In summary, the present invention provides an oil sorption article
that can be used both on land or water. The article is effective
for spilled oil around above ground tanks and pipes or, as shown in
the previous example, as a safeguard to prevent spilled oil from
penetrating into the ground around under ground storage tanks,
pipes or landfills. When used on an aqueous medium such as spilled
oil from an ocean tanker, the article will sorb many times its
weight, yet still remain afloat as a manageable conglomerate.
Although the present invention has been described with reference to
preferred embodiments, workers skilled in the art will recognize
that changes may be made in form and detail without departing from
the spirit and scope of the invention.
* * * * *